3. You are given 3 flasks (A<B and C) which are inoculated with E coli. A contain glucose, B contain glucose and lactose while C contains lactose. After 24 hours, which flask would contain beta_galactosidase?

a. A
b. B
c. C
d. A and B
e. B and C

My answer: e because lactose can be degraded to galactosidase.

4. Viroid contain

a. only RNA
b. only DNA
c. only protein
d. RNA and DNA

My answer: d
I read that viroid consist only of nucleic acid, not sure if it means DNA, RNA or both of them,

5. All the following are heavy metal used as antimicrobial agent except

a. iodine
b. merthiolate
c. selenium sulphate
d. copper sulphate

My answer: c.
I know b and d is correct. A is used as anti microbial agent but not sure if it is considered as heavy metal

For #3, I'm not entirely sure about this, but I think it should be C. I think it depends on how fast the E. Coli uses up the glucose. E. Coli should use up the glucose before using lactose as an energy source. If the glucose is used up before 24 hours, then E.coli should move on to lactose, allowing for the production of B-galactosidase. If not, then it shouldn't have B-galactosidase.

My guess is that the question should be testing for the understanding that glucose is used as an energy source before anything else, so I would think the answer is C.

As for the other questions, those are pretty much fact based and I'm too lazy to bother looking them up.